The production of polymers having improved processability utilizing metallocene catalyst systems in a solution phase polymerization process has been discussed in the art. For example, U.S. Pat. Nos. 5,272,236 and 5,380,810 describe a specific group of metallocene catalysts, namely monocylcopentadienyl metallocene systems, that are said to be capable of producing polymers having a high melt flow ratio and a narrow molecular weight distribution using a solution phase polymerization process. U.S Pat. No. 5,218,071 describes a solution process to produce a metallocene derived ethylene copolymer having a narrow molecular weight distribution and excellent flowability. EP-A1-0 683 184 published Nov. 22, 1995 describes a solution process using metallocenes to produce polymers having high viscous flow activation energies for good film moldability.
The gas phase production of polymers having improved processability using metallocene catalysts is known. For example, WO 95/07942 published Mar. 23, 1995 describes a gas phase fluidized bed process for producing ethylene polymers having improved processability using a monocyclopentadienyl transition metal metallocene catalyst compound and non-coordinating anion activator. EP-A2-0 452 920 published Oct. 23, 1991 describes a gas phase process for producing ethylene copolymers said to have a high melt tension and a narrow composition distribution using a prepolymerized catalyst system of a variety of metallocene catalyst compounds, including unbridged and bridged bis-cyclopentadienyl transition metal metallocene compounds.
EP-A1-0 659 773 published Jun. 28, 1995 describes a gas phase process for producing polyethylene at a certain temperature showing improved processability using an unsupported catalyst system of one or more bridged bis-cyclopentadienyl transition metal metallocene catalyst compounds. EP-A1-0 676 421 published Nov. 10, 1995 describes the gas phase production of polyolefins showing improved processability using a supported catalyst system of a bridged bis-cyclopentadienyl transition metal metallocene catalyst compound.
Thus, it would be highly desirable to have a gas phase polymerization process that produces polymers that have superior strength/toughness properties and have improved processability without the need for catalyst specificity.